1. Field of the Invention
The present invention relates to an apparatus for transmitting power. More particularly, the present invention relates to a variable damper that can variably regulate a power delivery characteristic between rotating bodies.
2. Description of the Related Art
Generally, a clutch disk utilized in a manual transmission includes a retaining plate, a driven plate, and a coulomb damper. The coulomb damper includes one or two friction discs and a pre-load spring applying a vertical load to a friction plate. The coulomb damper generates a constant hysteresis torque regardless of a twist angle of the damper. That is, a value of the hysteresis torque is constantly maintained regardless of an input sympathetic frequency or a vibration characteristic.
If the value of the hysteresis torque of the damper is small, a sympathetic phenomenon excessively occurs in a driving system and if the value of the hysteresis torque of the damper is big, a problem occurs that a transmission rate increases in a range of a high-numbered revolution.
That is, the hysteresis affects a vibration of the vehicle, for example, in a case where the sympathetic frequency of the engine is in resonance, an excessive booming noise occurs in the vehicle.
In this case, if the value of the hysteresis is big, the frequency of the engine can pass through a range of the resonance. However, in a case that the value of the hysteresis is in a normal running state, a problem occurs that an efficiency of the driving system is reduced.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.